The present invention relates to a jet printing ink composition which gives an image of high quality and which is stably jetted out.
Ink-jet printers have been widely used in not only offices but also homes with the spread of personal computers. As image-receiving material for ink-jet printer, ordinary paper, film and cloth have been used as well as paper specialized in ink-jet printing. On the other hand, as ink for ink-jet printing, oleaginous ink, aqueous ink and solid ink have been proposed. Practically, aqueous ink is mainly used because it less smells and is easy and safe to produce and deal with.
An aqueous ink is generally prepared by dissolving water-soluble dye in water. The aqueous ink comprising aqueous dye solution is excellent in transparency and color density, but is poor in water resistance and light resistance. Further, when printed on ordinary paper, the aqueous ink is apt to bleed to impair printing quality.
An aqueous ink comprising dispersed pigment or dye in place of water-soluble dye has been proposed (for example, in Japanese Patent Provisional Publication Nos. 56(1981)-157468, 4(1992)-18468, 10(1998)-110126 and 10(1998)-195355). This ink is improved in water resistance in some degree, but that resistance is still insufficient. Further, the dispersed pigment or dye is generally inferior to water-soluble dye in coloration. Furthermore, since the dispersion is unstable, the pigment or dye often chokes a jet nozzle.
Japanese Patent Provisional Publication No. 58(1983)-45272 describes dye enclosed in particles of urethane polymer latex. However, if the dye is enclosed in the particles to such an extent that sufficient density can be obtained, troubles on dispersion stability of the colored particles are often observed.
Further, the ink comprising dispersed pigment or dye is hardly spread and fixed on porous glossy paper. Recent ink jet printers often print images of photographic quality on porous photographic glossy paper. Accordingly, if the ink is insufficiently spread and fixed on the paper, the image has poor wear resistance.
An object of the present invention is to provide an aqueous ink which is excellent in coloration, which does not choke a jet nozzle, in which fine particles are stably dispersed, and particularly which is spread and fixed well on porous photographic glossy paper.
The present invention provides a jet printing ink composition containing a dye dissolved in an oil phase, which is emulsified in an aqueous medium, wherein the oil phase comprises an organic solvent having a boiling point of not lower than 150xc2x0 C., said oil phase having a viscosity in the range of 20 to 8,000 mPaxc2x7s at 25xc2x0 C., and wherein droplets of the emulsified oil phase have a volumetric average diameter of not larger than 100 nm.
The invention also provides a process for the preparation of a jet printing ink composition, which comprises the steps of: dissolving a dye in an organic solvent having a boiling point of not lower than 150xc2x0 C. to form an oil phase having a viscosity in the range of 20 to 8,000 mPaxc2x7s at 25xc2x0 C.; and then emulsifying the oil phase in an aqueous. medium to form droplets of the oil phase having a volumetric-average diameter of not larger than 100 nm.
The invention further provides an ink-jet recording method in which an image is recorded with ink drops on an image-receiving material, said image-receiving material comprising a support and an image-receiving layer containing white inorganic pigment particles, and said ink drops being jetted out according to recording signals, wherein the ink drops consist of a jet printing ink composition containing a dye dissolved in an oil phase, which is emulsified in an aqueous medium, and wherein the oil phase comprises an organic solvent having a boiling point of not lower than 150xc2x0 C., said oil phase having a viscosity in the range of 20 to 8,000 mPaxc2x7s at 25xc2x0 C., and wherein droplets of the emulsified oil phase have a volumetric average diameter of not larger than 100 nm.
The jet printing ink composition of the invention is an emulsion in which droplets of an oil phase are emulsified in an aqueous medium.
The term xe2x80x9caqueous mediumxe2x80x9d means water or a mixture of water and an organic solvent, which is miscible with water. The aqueous medium can further contain additives such as a surfactant, a wetting agent, a stabilizing agent and an antiseptic.
The oil phase can be obtained by dissolving an oleaginous dye in a water-incompatible organic solvent having a high boiling point (which is not lower than 150xc2x0 C.). The oil phase can contain, if needed, additives such as an ultraviolet absorbing agent, an oxidation inhibitor, a stabilizing agent and a viscosity adjusting agent.
The oil phase has a specific gravity preferably in the range of 0.90 to 1.15 at 25xc2x0 C., more preferably in the range of 0.95 to 1.10 at 25xc2x0 C., and most preferably in the range of 0.95 to 1.05 at 25xc2x0 C.
The oil phase has a viscosity in the range of 20 to 8,000 mPaxc2x7s, preferably in the range of 100 to 4,000 mPaxc2x7s, and more preferably in the range of 200 to 3,000 mPaxc2x7s. If the viscosity is too high, the ink is hardly spread and fixed on porous photographic glossy paper, and accordingly the wear resistance of printed image is impaired.
The viscosity of the oil phase can be measured according to known methods (for example, described in xe2x80x9cJIKKEN KAGAKU KOZAxe2x80x9d, 4th edition, pp.113). It can be also measured by means of a commercially available viscometer (e.g., rotating-vibrating viscometer).
The viscosity of the oil phase can be controlled by the amount of the organic solvent dissolving the oleaginous dye and/or by selecting the solvent and the dye. The viscosity of the organic solvent directly affects that of the oil phase. Further, the oil phase having a low viscosity can be obtained by using an oleaginous dye having a molecular structure in which many ester linkages or ether linkages are contained and rotation between Cxe2x80x94C or C-hetero atom is restricted in a small degree.
The oleaginous dye preferably has a water-solubility of not more than 1 wt.%.
Examples of yellow dye include aryl azo dyes, hetero aryl azo dyes, azomethine dyes, methine dyes and quinone dyes. The aryl azo dyes and the hetero aryl azo dyes can have, as a coupling component, phenols, naphthols, anilines, pyrazolones, pyridones or open-chained active methylene compounds. The azomethine dyes can have open-chained active methylene compounds as a coupling component. The methine dyes include benzylidene dyes and monomethine oxonol dyes. The quinone dyes include naphthoquinone dyes and anthraquinone dyes.
Further, quinophthalone dyes, nitro dyes, nitroso dyes, acridine dyes and acridinone dyes can be also used as yellow dye. A dye whose chromophore partially dissociates to give yellow color can be also used as yellow-dye. In that dye, a counter cation for dissociation may be either an inorganic cation (e.g., alkali metal ion, ammonium ion) or an organic cation (e.g., pyridinium ion, quaternary ammonium ion). Further, a polymer cation having a partial structure of cation can be used as a counter cation.
Examples of magenta dye include aryl azo dyes, hetero aryl azo dyes, azomethine dyes, methine dyes, carbonium dyes, quinone dyes and condensed pqlycyclic dyes. The aryl azo dyes and the hetero aryl azo dyes can have phenols, naphthols and anilines as a coupling component. The azomethine dyes can have, as a coupling component, pyrazolones and pyrazolotriazole open-chained active methylene compounds. The methine dyes include arylidene dyes, styryl dyes, merocyanine dyes and oxonol dyes. The carbonium dyes include diphenylmethane dyes, triphenylmethane dyes and xanthene dyes. The quinone dyes include anthraquinone dyes and anthrapyridone dyes. The condensed polycyclic dyes include dioxadine dyes.
A dye whose chromophore partially dissociates to give magenta color can be also used as magenta dye. In that dye, a counter cation for dissociation may be either an inorganic cation (e.g., alkali metal ion, ammonium ion) or an organic cation (e.g., pyridinium ion, quaternary ammonium ion). Further, a polymer cation having a partial structure of cation can be used as a counter cation.
Examples of cyan dye include azomethine dyes, polymethine dyes, carbonium dyes, phthalocyanine dyes, anthraquinone dyes, aryl azo dyes, hetero aryl azo dyes, indigo dyes and thioindigo dyes. The azomethine dyes include indoaniline dyes and indophenol dyes. The polymethine dyes include cyanine dyes, oxonol dyes and merocyanine dyes. The carbonium dyes include diphenylmethane dyes, triphenylmethane dyes and xanthene dyes. The aryl azo dyes and the hetero aryl azo dyes can have, as a coupling component, phenols, naphthols and anilines.
A dye whose-chromophore partially dissociates to give cyan color can be also used as cyan dye. In the dye, a counter cation for dissociation may be either an inorganic cation (e.g., alkali metal ion, ammonium ion) or an organic cation (e.g., pyridinium ion, quaternary ammonium ion). Further, a polymer cation having a partial structure of cation can be used as a counter cation.
Examples of preferred oleaginous dye include the following dyes set forth in color index (C.I.): solvent black 3, 7, 27, 29, 34; solvent yellow 14, 16, 19, 29, 30, 56, 82, 93, 162; solvent red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132, 218; solvent violet 3; solvent blue 2, 11, 25, 35, 70; solvent green 3, 7; solvent orange 2; disperse yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184:1, 186, 198, 199, 201, 204, 224, 237; disperse orange 13, 29, 31:1, 33, 49, 54, 55, 66, 73, 118, 119, 163; disperse red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167:1, 177, 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356, 362; disperse violet 33; disperse blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165:1, 165:2, 176, 183, 185, 197, 198, 201, 214, 224, 225, 257, 266, 267, 287, 354, 358, 365, 368; and disperse green 6:1, 9.
Commercially available oleaginous dyes (e.g., Nubian Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scarlet 308, Vali Fast Blue 2606, Oil Blue BOS [Orient Chemicals Co., Ltd.]; Neopan Yellow 075, Neopan Magenta SE1378, Neopan Blue 808, Neopan Blue FF4012, Neopan Cyan FF4238 [BASF]) are also usable.
The oleaginous azomethine dye represented by the following formula (I) is preferred. 
In the formula (I), R1 is hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR11, xe2x80x94SR12, xe2x80x94COOR13, xe2x80x94OCOR14, xe2x80x94NR15R16, xe2x80x94CONR17R18, xe2x80x94SO2R19, xe2x80x94SO2NR20R21, xe2x80x94NR22CONR23R24, xe2x80x94NR25COOR26, xe2x80x94COR27, xe2x80x94NR28COR29 or xe2x80x94NR30SO2R31 in which each of R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R28, R29, R30 and R31 is independently hydrogen atom, an aliphatic group or an aromatic group; A is hydroxyl or xe2x80x94NR4R5 in which each of R4 and R5 is independently hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group; X1 is xe2x95x90C(R6)xe2x80x94 or xe2x95x90Nxe2x80x94; X2 is xe2x80x94C(R7)xe2x95x90 or xe2x80x94Nxe2x95x90; each of R2, R3, R6 and R7 is independently hydrogen atom, a halogen atom, an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR51, xe2x80x94SR52, xe2x80x94COOR53, xe2x80x94OCOR54, xe2x80x94NR55R56, xe2x80x94CONR57R58, xe2x80x94SO2R59, xe2x80x94SO2NR60R61, xe2x80x94NR62CONR63R64, xe2x80x94NR65COOR66, xe2x80x94COR67, xe2x80x94NR68COR69 or xe2x80x94NR70SO2R71 in which each of R51, R52, R53, R54, R55, R56, R57, R58, R59, R60, R61, R62, R63, R64, R65, R66, R67, R68, R69, R70 and R71 is independently hydrogen atom, an aliphatic group or an aromatic group; each combination of R2 and R3, R3 and R4, R4 and R5, R5 and R6, and R6 and R7 may be combined to form a ring; Z is an atomic group forming a 5- or 6-membered nitrogen-containing heterocyclic ring which may be substituted with an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR81, xe2x80x94SR82, xe2x80x94COOR83, xe2x80x94OCOR84, xe2x80x94NR85R86, xe2x80x94CONR87R88, xe2x80x94SO2R89, xe2x80x94SO2NR90R91, xe2x80x94NR92CONR93R94, xe2x80x94NR95COOR96, xe2x80x94COR97, xe2x80x94NR98COR99 or xe2x80x94NR100SO2R101 in which each of R81, R82, R83, R84, R85, R86, R87, R88, R89, R90, R91, R92, R93, R94, R95, R96, R97, R98, R99, R100 and R101 is independently hydrogen atom, an aliphatic group or an aromatic group; and the nitrogen-containing heterocyclic ring may be condensed with another ring.
In the formula (I), Z is preferably xe2x80x94Y2xe2x95x90Y1xe2x80x94Nxe2x95x90. Here, one of Y1 and Y2 is xe2x80x94C(R8)xe2x95x90 and the other is xe2x80x94Nxe2x95x90 in which R8 is hydrogen atom, an aliphatic group or an aromatic group.
In the formula (I), A is preferably xe2x80x94NR4R5.
An oleaginous pyrazoloazole azomethine dye represented by the following formula (II) is more preferred. 
In the formula (II), each of R1, R2, R3, R4, R5, R6 and R7 is the same as that defined for the formula (I).
In the formula (II), one of Y1 and Y2 is xe2x80x94C(R8)xe2x95x90 and the other is xe2x80x94Nxe2x95x90 in which R8 is hydrogen atom, an aliphatic group or an aromatic group. It is particularly preferred that Y1 and Y2 be xe2x80x94C(R8)xe2x95x90 and xe2x80x94Nxe2x95x90, respectively.
In the formula (I), R1 is hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR11, xe2x80x94SR12, xe2x80x94COOR13, xe2x80x94OCOR14, xe2x80x94NR15R16, xe2x80x94CONR17R18, xe2x80x94SO2R19, xe2x80x94SO2NR20R21, xe2x80x94NR22CONR23R24, xe2x80x94NR25COOR26, xe2x80x94COR27, xe2x80x94NR28COR29 or xe2x80x94NR30SO2R31 in which each of R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23, R24, R25, R26, R27, R28, R29, R30 and R31 is independently hydrogen atom, an aliphatic group or an aromatic group.
R1 preferably is hydrogen atom, an aliphatic group, an aromatic group, xe2x80x94OR11, xe2x80x94SR12, xe2x80x94NR15R16, xe2x80x94SO2R19, xe2x80x94NR22xe2x80x94CONR23R24, xe2x80x94NR25COOR26, xe2x80x94NR28COR29 or xe2x80x94NR30SO2R31; more preferably is hydrogen atom, an aliphatic group, an aromatic group, xe2x80x94OR11 or xe2x80x94NR15R16; further preferably is hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an alkoxy group, a substituted alkoxy group, a phenoxy group, a substituted phenoxy group, a dialkylamino group or a substituted dialkylamino group; furthermore preferably is hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a substituted alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or a substituted aryl group having 6 to 10 carbon atoms; and most preferably is hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a substituted alkyl group having 1 to 6 carbon atoms.
In the present specification, the term xe2x80x9can aliphatic groupxe2x80x9d means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group or a substituted aralkyl group.
The alkyl group may have a branched or cyclic structure. The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 18 carbon atoms.
The alkyl moiety of the substituted alkyl group is the same as the alkyl group described above.
The alkenyl group may have a branched or cyclic structure. The alkenyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 18 carbon atoms.
The alkenyl moiety of the substituted alkenyl group is the same as the alkenyl group described above.
The alkynyl group may have a branched or cyclic structure. The alkynyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 18 carbon atoms.
The alkynyl moiety of the substituted alkynyl group is the same as the alkynyl group described above.
The alkyl moiety of the aralkyl group or the substituted aralkyl group is the same as the alkyl group described above. The aryl moiety of the aralkyl group or the substituted aralkyl group is the same as the aryl group described below.
Examples of the substituent group of the alkyl moiety of the substituted alkyl group, the substituted alkenyl group, the substituted alkynyl group or the substituted aralkyl group include a halogen atom, cyano, nitro, a heterocyclic group, xe2x80x94OR111, xe2x80x94SR112, xe2x80x94COOR113, xe2x80x94NR114R115, xe2x80x94CONR116R117, xe2x80x94SO2R118 and xe2x80x94SO2NR119R120 in which each of R111, R112, R113, R114, R115, R116, R117, R118, R119 and R120 is independently hydrogen atom, an aliphatic group or an aromatic group.
Examples of the substituent group of the aryl moiety of the substituted aralkyl group are the same as those of the substituted aryl group described below.
In the present specification, the term xe2x80x9can aromatic groupxe2x80x9d means an aryl group or a substituted aryl group.
The aryl group is preferably phenyl or naphthyl, more preferably phenyl.
The aryl moiety of the substituted aryl group is the same as the aryl group described above.
Examples of the substituent group of the substituted aryl group include a halogen atom, cyano, nitro, an aliphatic group, a heterocyclic group, xe2x80x94OR121, xe2x80x94SR122, xe2x80x94COOR123, xe2x80x94NR124R125, xe2x80x94CONR126R127, xe2x80x94SO2R128 and xe2x80x94SO2NR129R130 in which each of R121, R122, R123, R124, R125, R126, R127, R128, R129 and R130 is independently hydrogen atom, an aliphatic group or an aromatic group.
In the present specification, the heterocyclic group preferably contains a 5- or 6-membered saturated or unsaturated heterocyclic ring which may be condensed with an aliphatic ring, an aromatic ring or another heterocyclic ring. Examples of the hetero atom in the heterocyclic ring include B, N, O, Se and Te. A preferred hetero atom is N, O or S. The heterocyclic ring preferably has a monovalent carbon atom (through which the heterocyclic group is combined). Examples of the saturated heterocyclic ring include pyrrolidine ring, morpholine ring, 2-bora-1,3-dioxolan ring and 1,3-thiazolidine ring. Examples of the unsaturated heterocyclic ring include imidazole ring, thiazole ring, benzothiazole ring, benzoxazole ring, benzotriazole ring, benzoselenazole ring, pyridine ring, pyrimidine ring and quinoline ring.
The heterocyclic group may have a substituent. Examples of the substituent include a halogen atom, cyano, nitro, an aliphatic group, an aromatic group, a heterocyclic group, xe2x80x94OR131, xe2x80x94SR132, xe2x80x94COOR133, xe2x80x94NR134R135, xe2x80x94CONR136R137, xe2x80x94SO2R138 and xe2x80x94SO2NR139R140 in which each of R131, R132, R133, R134, R135, R136, R137, R138, R139 and R140 is independently hydrogen atom, an aliphatic group or an aromatic group.
In the formula (I), A is hydroxyl or xe2x80x94NR4R5, and xe2x80x94NR4R5 is preferred to hydroxyl. Each of R4 and R5 is independently hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group; preferably is hydrogen atom or an aliphatic group; more preferably is hydrogen atom, an alkyl group or a substituted alkyl group; and most preferably is hydrogen atom, an alkyl group having 1 to 18 carbon atoms or a substituted alkyl group having 1 to 18 carbon atoms.
In the formula (I), X1 is xe2x95x90C(R6)xe2x80x94 or xe2x95x90Nxe2x80x94, and X2 is xe2x80x94C(R7)xe2x95x90 or xe2x80x94Nxe2x95x90. One of X1 and X2 is preferably xe2x95x90C(R6)xe2x80x94 or xe2x80x94C(R7)xe2x95x90. More preferably, X1 is xe2x95x90C(R6)xe2x80x94 and X2 is xe2x80x94C(R7)xe2x95x90.
In the formula (I), each of R2, R3, R6 and R7 is independently hydrogen atom, a halogen atom, an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR51, xe2x80x94SR52, xe2x80x94COOR53, xe2x80x94OCOR54, xe2x80x94NR55R56, xe2x80x94CONR57R58, xe2x80x94SO2R59, xe2x80x94SO2NR60R61, xe2x80x94NR62CONR63R64, xe2x80x94NR65COOR66, xe2x80x94COR67, xe2x80x94NR68COR69 or xe2x80x94NR70SO2R71 in which each of R51, R52, R53, R54, R55, R56, R57, R58, R59, R60, R61, R62, R63, R64, R65, R66, R67, R68, R69, R70 and R71 is independently hydrogen atom, an aliphatic group or an aromatic group.
Each of R2 and R7 preferably is independently hydrogen atom, a halogen atom, an aliphatic group, xe2x80x94OR51, xe2x80x94NR62COxe2x80x94NR63R64, xe2x80x94NR65COOR66, xe2x80x94NR68COR69 or xe2x80x94NR70SO2R71; more preferably is hydrogen atom, fluorine atom, chlorine atom, an alkyl group, a substituted alkyl group, xe2x80x94NR62CONR63R64 or xe2x80x94NR68COR69; further preferably is hydrogen atom, chlorine atom, an alkyl group having 1 to 10 carbon atoms and a substituted alkyl group having 1 to 10 carbon atoms; most preferably is hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a substituted alkyl group having 1 to 4 carbon atoms.
Each of R3 and R6 preferably is independently hydrogen atom, a halogen atom or an aliphatic group; more preferably is hydrogen atom, fluorine atom, chlorine atom, an alkyl group or a substituted alkyl group; further preferably is hydrogen atom, chlorine atom, an alkyl group having 1 to 10 carbon atoms and a substituted alkyl group having 1 to 10 carbon atoms; and most preferably is hydrogen atom, an alkyl group having 1 to 4 carbon atoms and a substituted alkyl group having 1 to 4 carbon atoms. In the formula (I), each combination of R2 and R3, R3 and R4, R4 and R5, R5 and R6, and R6 and R7 may be combined to form a ring. The set of R3 and R4, R4 and R5, or R5 and R6 preferably forms a ring.
The ring formed by the set of R2 and R3 or the set of R6 and R7 is preferably a 5- or 6-membered ring. The ring is preferably an aromatic ring (e.g., benzene ring) or an unsaturated heterocyclic ring (e.g., pyridine ring, imidazole ring, thiazole ring, pyrimidine ring, pyrrole ring, furan ring).
The ring formed by the set of R3 and R4 or the set of R5 and R6 is preferably a 5- or 6-membered ring, examples of which include tetrahydroquinoline ring and dihydroindole ring.
The ring formed by the set of R4 and R5 is preferably a 5- or-6-membered ring, examples of which include pyrrolidine ring, piperidine ring and morpholine ring.
In the formula (I), Z is an atomic group forming a 5- or 6-membered nitrogen-containing heterocyclic ring. Preferably, Z forms a 5-membered nitrogen-containing heterocyclic ring. Examples of the 5-membered nitrogen-containing heterocyclic ring include imidazole ring, triazole ring and tetrazole ring. Preferred is triazole ring, and more preferred is the triazole ring represented by the formula (II).
The nitrogen-containing heterocyclic ring may be substituted with an aliphatic group, an aromatic group, a heterocyclic group, cyano, xe2x80x94OR81, xe2x80x94SR82, xe2x80x94COOR83, xe2x80x94OCOR84, xe2x80x94NR85R86, xe2x80x94CONR87R88, xe2x80x94SO2R89, xe2x80x94SO2NR90R91, xe2x80x94NR92CONR93R94, xe2x80x94NR95COOR96, xe2x80x94COR97, xe2x80x94NR98COR99 or xe2x80x94NR100SO2R101. Each of R81, R82, R83, R84, R85, R86, R87, R88, R89, R90, R91, R92, R93, R94, R95, R96, R97, R98, R99, R100 and R101 is independently hydrogen atom, an aliphatic group or at aromatic group. The nitrogen-containing heterocyclic ring may be condensed with another ring. The nitrogen-containing heterocyclic ring may be condensed with another ring.
In the formula (II), each of Y1 and Y2 is independently xe2x80x94C(R8)xe2x95x90 or xe2x80x94Nxe2x95x90 in which R8 is hydrogen atom, an aliphatic group or an aromatic group. R8 preferably is hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group or a substituted aryl group; more preferably is hydrogen atom; a substituted alkyl group having 1 to 150 carbon atoms or a substituted aryl group having 6 to 150 carbon atoms; and most preferably is a substituted alkyl group having 1 to 100 carbon atoms or a substituted aryl group having 6 to 100 carbon atoms. In the case where each of Y1 and Y2 is xe2x80x94C(R8)xe2x95x90, the two R8s may be combined to form a ring. The ring is preferably a 6-membered ring, and is preferably an aromatic ring (e.g., benzene ring).
It is particularly preferred that Y1 and Y2 be xe2x80x94C(R8)xe2x95x90 and xe2x80x94Nxe2x95x90, respectively.